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Microbial correlates of Fusarium biomass and deoxynivalenol content in individual wheat seeds

Matthew Bakker: USDA ARS

<div>Fusarium head blight is associated with mycotoxin accumulation in grain, which is a food safety hazard. Aiming to identify novel management approaches for this problem, we used qPCR, gas chromatography, and amplicon sequencing to examine correlations between <em>Fusarium</em> biomass or deoxynivalenol (DON) content and characteristics of the microbial communities inhabiting wheat grain. Microorganisms inhabiting the wheat seed could lessen DON content by reducing <em>Fusarium</em> biomass, or by lowering DON production per unit <em>Fusarium</em> biomass. Samples were collected from a common wheat variety planted across a mist irrigated nursery in St. Paul, Minnesota, in each of two successive years. Individual seeds were analyzed in an attempt to approach the fine spatial scale at which microbial communities are organized. Out of 96 seeds tested in 2016, both <em>Fusarium</em> and DON were present at measurable levels in every seed tested. Out of 192 seeds tested in 2017, DON was detected in only 27% of seeds. Where measurable, relationships between <em>Fusarium</em> biomass and DON content were strong (r<sup>2</sup>=0.78 in 2016 and 0.72 in 2017; <em>P</em><0.001). Microbiome profiles revealed that for certain taxa, abundance among seeds was correlated with pathogen biomass or with the deviation from the expected relationship between <em>Fusarium</em> biomass and DON content. Seeds collected from the same head harbored microbiomes that were on average more similar to each other than seeds collected from different heads. This indicates some biogeographic patterning to the assembly of the wheat spike microbiome. The microbial communities associated with wheat seeds have the potential to substantially impact the development of Fusarium head blight and the accumulation of mycotoxins in grain. With rigorous technology development, the microbiome of wheat heads may become a target for agricultural management.</div>

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